Optimising methodology for tongue swab testing for Mycobacterium tuberculosis complex (Mtbc) in an outpatient setting in Malawi, version 1.0
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Date
2022-05-30
Authors
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Kamuzu University of Health Sciences
Abstract
The type of research study
A diagnostic evaluation
The problem to be studied
Research undertaken to optimise using oral swabs to diagnose Mycobacterium tuberculosis complex
(Mtbc) has not resulted in widely accepted, reliable and reproducible methods. We will use
previously reported methods in the literature combined with commercially available swabs and
media to produce a swabbing methodology that can be reproduced to test accuracy in a clinical
setting. The study will aim to look at analytical validity of a swabbing methodology.
Broad Objective
To optimise the methodology of collecting and analysing tongue swabs to diagnose Mtbc and the
acceptability and feasibility to individuals in a clinic setting in Malawi.
Specific Objectives
1. Evaluate the limit of detection of PCR for Mtbc compared to Xpert Ultra in a series of spiked
with Mtbc at different dilutions.
2. To evaluate the feasibility and acceptability of healthcare worker (HCW) and self-taken
tongue swabs to diagnose Mtbc using the Xpert Ultra cartridge in a sample of adults with
microbiologically confirmed PTB.
3. To compare detection of Mtbc from tongue swabs when analysed using Xpert Ultra versus
manual PCR in a sample of adults with microbiologically confirmed PTB.
Methodology
Participants in the study will be adults at Queen Elizabeth Hospital, Blantyre with confirmed
pulmonary TB. Individuals positive on Xpert Ultra sputum test for TB attending clinic to initiate
treatment will be recruited. Participants will be consented then invited to complete a questionnaire
to assess clinical history and symptoms. They will then be asked to have two tongue swabs taken
(one by the participant and one by a healthcare worker). They will then be asked a short
questionnaire on their experience of sampling (Figure 1: Study clinic workflow). Samples will be
labelled and transported to the MLW/KUHeS TB Laboratory for processing by Xpert Ultra with
remaining sample frozen for analysis by PCR (DNA extracted using PrimeXtract kit and stored until
testing with Primestore qPCR). All DNA extraction and qPCR will be conducted at the MLW/KUHeS
TB Laboratory, following the study SOP. Expected Findings and their dissemination
We expect to identify a new methodology for collecting and processing tongue swabs that is likely to
have lower sensitivity than Xpert Ultra on sputum, but sufficiently accuracy for screening rapid
screening purposes. We do not expect there to be a difference between self-taken and healthcare
worker taken swabs. Results will be presented at local meetings both in Liverpool and Malawi and
shared with COMREC. They will be further presented at national and international conferences such
as Union world conference on Lung Health. The final aim will be to publish in a peer reviewed journal. Results will be prepared in a visual format accessible to participants and presented either at
community meetings or displayed in the clinic in the context of COVID-19.
Description
The type of research study
A diagnostic evaluation